Lighting devices that include conversion materials may conveniently allow the conversion of light from a source light into light of a different wavelength range. Often, such conversion may be performed by using a luminescent, fluorescent, or phosphorescent material. These wavelength conversion materials may sometimes be included in the bulk material of another object, applied to a lens or optic, or otherwise located in line with the light emitted from a light source and a space to be illuminated. In some instances the conversion material may be applied to the light source itself. A number of disclosed inventions exist that describe lighting devices that utilize a conversion material applied to an LED to convert light with a source wavelength range into light of a converted wavelength range.
However, to achieve a desired chromaticity of converted light, such as, for example, a warm white light, a substantial amount of phosphor conversion materials may be required to produce a light within a desired wavelength range. For example, yellow and red phosphor conversion coatings are used in combination to create warm white light. However, using a plurality of phosphor coatings may result in double conversion of light due to luminous flux. This double conversion may best be illustrated in FIGS. 15-16 of this disclosure.
Referring to FIG. 15, an illustrative dual characteristic color conversion that may be performed according to the prior art will now be discussed. In this illustrative conversion, a plurality of phosphor conversion materials may be included on or in an enclosure to perform a plurality of color conversion to the source light. However, the phosphors may perform repeated color conversions on overlapping wavelength ranges of source light.
For example, a first phosphor may absorb essentially the wavelength range of source light, as indicated by the first range 78. This wavelength range may correspond with a yellow phosphor. A second phosphor may absorb a different, but partially overlapping wavelength range of source light, as indicated by the second range 79. This wavelength range may correspond with a red phosphor. The second range 79 may overlap a substantial portion of the source wavelength range, allowing the second phosphor to convert at least part of the source light left unconverted by the first phosphor. However, the second phosphor may also convert a significant portion of light that has already been converted by the first phosphor. This double conversion wastes energy and reduces efficiency. As illustrated by the waveform 76 of FIG. 16, the converted light may have an approximately white chromaticity but lack the luminosity of an efficient lighting device.
This double conversion can result in substantial losses of lighting efficacy (lumens/watt), on the order of thirty to forty percent. Additionally, phosphor materials may also inefficiently absorb the high energy wavelength range of blue light, leaving an undesired residual wavelength range of unconverted light.
In the past, proposed solutions have attempted to use conversion materials that included a plurality of wide production conversion materials, such as phosphors to convert a source light into a converted light prior to illuminating a space with a desired color of light. However, including additional the conversion materials does not address the inefficiency caused by the wide conversion wavelength range characteristics double conversion operation due to performing a plurality of wide production conversion operations.
Also, LEDs and other lighting elements may generate heat during operation. Applying a conversion material directly upon a lighting element may cause the material to be exposed to an excessive amount of heat resulting in decreased operational efficiency of the conversion material.
There exists a need for an enclosure for lighting devices that provides an ability to receive a light emitted from a light source in one wavelength range, convert the source light into a converted light within a converted wavelength range by performing a wide production wavelength conversion and a narrow production wavelength conversion, and direct the converted light in a desired output direction. There further exists a need for a light converting device that performs the wavelength conversion operation away from a heat generating light source.